Potential changes in riverine biogeochemistry with land cover shifts at the receding Wolverine Glacier, southcentral Alaska
Abstract
The Wolverine Glacier (550-1500 m), on the Kenai Peninsula on the south-central Alaska coast, is a fast-receding alpine glacier. The 15-km2 glacier occupies about 50 percent of its watershed, and the remaining land cover is alpine tundra dotted with lakes, grading into shrubifying landscape at lower elevations. Wolverine Creek drains the glacier and flows 1 km downstream to a USGS streamgage, and another 1.5 km to the Nellie Juan River, which flows 15 km to Prince William Sound. The lower Nellie Juan is forested in White Spruce and Western Hemlock. The objective of our study is to quantify solute fluxes from the contrasting land covers (glacial ice and snow, tundra, shrubifying land, and forest), project how these fluxes may shift as the glacier recedes and the other land covers increase, and evaluate potential effects on marine nutrient subsidies. In 2019 we deployed recording water quality sondes at representative streams in the four land cover types, and at the integrative sites of Wolverine Creek (at streamgage) and lower Nellie Juan. Discrete water quality samples for major ions and Dissolved Organic Matter (DOM) were collected during approximately monthly site visits. Sub-glacial and groundwater-dominated high-conductance waters at the start of melt shifted to more dilute meltwater though summer. DOM, as inferred from sensor fluorescence, was low in glacial runoff, but its yield was high given the high meltwater volume. Earlier work at Wolverine (incubations measuring lost DOM) and high Fluorescence Index (FI) in our discrete glacial runoff samples suggest this glacial DOM is biolabile, consistent with studies in southeastern Alaska, where glacial DOM was readily incorporated into freshwater and marine food webs. DOM from the other land types was more humic and refractory, but late summer and fall storms revealed episodic DOM concentrations that tracked the high flows, with the forest and shrub land covers showing the greatest DOM response. Particulate carbon in discrete glacial runoff samples correlated strongly with its high turbidity, and showed concentrations near 2 mg/L compared to DOM-C of 1 mg/L. The glacial landscape exports calcium, iron, and dissolved and particulate carbon to the nearshore ocean. These terrestrial subsidies to the marine ecosystem may diminish as glacial runoff diminishes.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFM.H25S1239S